Question

We have a Java web application that uses Spring and Hibernate and has a fairly standard architecture. Currently the application supports SOAP based clients in addition to a Flex GUI client that communicates via AFM/HTTP to a BlazeDS backend. Today the application runs only in Tomcat, but support for JBoss and Websphere is forthcoming.

We are now being to ensure that the application can run in a clustered environment for the purposes of scalability and failover. This question is primarily about the Java application server tier (rather than the database tier). Other than login session information that is managed by Spring Security, the application is stateless.

What do we need to consider when supporting a clustered environment?

Looking for any tips around logging, JNDI, configuration, file I/O, login sessions, etc. — anything!

Answer 1

• If you have file I/O, make sure to use semaphores/something similar to make sure the I/O operations happen the way you want them to.
• If you are using any SSO (single sign-on) products, make sure they work properly after clustering.
• SSL certificates must be installed/maintained on all servers.
• If you are using JBoss, either mod_cluster or mod_proxy can be used, depending on your environment/requirements.
• If you are using WebSphere, you can install the deployment manager on one of the physical machines where one node is present.
• Test your images and other static resources thoroughly to make sure they all work properly.
• Keep the logs separate for each server.
• I am not sure if you are using any load balancers – just make sure that the load is distributed somewhat evenly between the servers.
• All the standard stuff: session management, authentication, etc.